1. Field of the Invention
The present invention relates generally to pressure regulators and, more particularly to, a dielectric fitting for a pressure regulator.
2. Description of the Related Art
Pressure regulators are configured to produce a desired output pressure of a fluid from an input pressure of the fluid. Often, pressure regulators are configured to reduce the input pressure so that the output pressure is substantially less than the input pressure.
Single stage and dual stage pressure regulators are available to reduce the input pressure. Single stage regulators are often employed to regulate fluid pressure in gas appliances such as gas grills. Dual stage pressure regulators are often employed for regulating fluid pressure of natural gas or propane in domestic fluid systems. For instance, one dual stage pressure regulator has a first stage that reduces the fluid pressure from a storage tank, such as a propane storage tank, to around 10 psi, while a second stage reduces the 10 psi input to around 11 inches water column output pressure. Some regulations require the output pressure not to exceed 2 psi.
Typically, pressure regulators include a housing formed of upper and lower housing portions that are connected together with fasteners and a diaphragm located between the upper and lower housing portions. An outer periphery of the diaphragm often has a lip shaped to fit inside an annular recess in the lower housing portion to help seal between the upper and lower housing portions. Generally, the diaphragm of the pressure regulator is shaped to have an inner annular section configured to raise and lower during operation of the pressure regulator. The diaphragm has a flexible connecting section radially extending between the inner annular section and the outer lip. The flexible connecting section has a thickness less than a thickness of the inner annular section and the lip. A diaphragm plate is positioned on top of the inner annular section to provide additional rigidity to the inner annular section as the inner annular section raises and lowers during operation. In some conventional pressure regulators, projections on the lower housing portion suspend a bottom surface of the inner annular section of the diaphragm above an inner surface of the lower housing portion to reduce contact between the bottom surface and the lower housing portion.
Generally, the pressure regulator includes a valve body disposed in the lower housing portion and is slidable among a plurality of operational positions. Typically, a valve disc is retained by the valve body. The valve disc is configured to engage a valve seat surrounding a fluid passageway when the valve body is in a closed position. When the valve disc and valve body are spaced from the valve seat, fluid passes through the passageway into a pressure chamber of the lower housing portion. A lever operatively couples the diaphragm with the valve body. When the input pressure pushes the valve disc and valve body away from the valve seat to allow fluid to pass through the passageway, pressure in the pressure chamber increases, and the diaphragm rises. As the diaphragm rises, the lever pivots about a pivot point and urges the valve body and valve disc back toward the valve seat. This reduces the amount of fluid that passes through the passageway and reduces the pressure in the pressure chamber. This back and forth action results in pressure regulation by regulating fluid flow through the passageway, around the valve body, and into the pressure chamber.
In a gas pressure regulator, an integral dielectric connection may be provided to electrically isolate an inlet piping from an outlet piping. When this occurs, it eliminates the need for additional components such as an electrically isolating union and the associated additional leak points. The electrical isolation prevents the galvanic corrosion associated with buried metallic piping connected to piping of dissimilar metals in a dwelling. The electrical isolation provides a degree of safety in the event that buried piping contacts underground electrical conductors by electrically isolating piping that enters a dwelling.
In some constructions, the dielectric connection may include a metallic insert and a polymer over-molded onto the metallic insert. Over-molding a bonded polymer onto a metallic insert can produce a component with a desirable combination of mechanical strength and electrical properties. However, there are substantial differences between individual injection molded polymeric components and composite construction consisting of an over-molded polymeric material bonded to a metallic insert. These differences provide distinct advantages and substantial benefits to the present invention.
When over-molding a metal insert with a bonded polymer, the types and grades of polymers, and therefore the range of mechanical and electrical performance characteristics, is limited to those that are compatible with, and capable of, adhering to the insert material. Components that are not over-molded are not subject to such material limitations.
The process of over-molding a metal insert with a bonded polymer introduces numerous manufacturing variables that can lead to defects and functional failures. These failures can include delamination of the polymer from the insert due to improper insert handling or preparation, reduced electrical insulating capability or structural failures including fluid leakage or failure to contain pressure due to defects in the over-molded polymer such as porosity and pin-holes caused by out-gassing of the insert during molding, variation in polymer thickness due to variation in both location of the insert within the over-molding tool and the tolerances associated with manufacturing metallic inserts. Polymeric components that are not over-molded on metallic inserts are not subject to these defects and failure modes.
The cost of over-molding a metallic insert with a bonded polymer can be relatively high due to the increased time required to cool the insert to the solidification temperature of the polymer during molding. Since the cooling time required for over-molding polymers is dependent on the thickness of the assembly being molded, and since cooling time can be in the range of 20 to 40 seconds for each 0.100 of an inch in thickness, it can take in excess of 100 seconds to over-mold a 0.050 inch thick polymer on both sides of a 0.250 inch thick insert. Since the cooling time for a 0.050 inch thick polymeric part that is not over-molded would be in the range of 10 to 20 seconds, it can be manufactured at substantially lower cost.
A metal insert that is over-molded with a bonded insulating polymer has the disadvantage of not being serviceable in the field. The entire over-molded assembly must be replaced which can make maintenance and repairs more complicated and expensive. Construction that is not over-molded allows the field replacement of individual insulating components in the event of damage or wear.
In addition, without some time of reinforcement, the over-molded insulating polymer may relax and loose its sealing to the metallic insert over time. Also, without some type of load distribution on the over-molded insulating polymer, a concentrated force under mechanical load may cause deflection of the over-molded insulating polymer, leading to leaks at the connection with the metallic insert. Further, without a drip line, the over-molded insulating polymer on the metallic insert may allow water to enter that could defeat the dielectric function.
Therefore, it is desirable to provide a pressure regulator with a new dielectric construction that electrically isolates an inlet piping from an outlet piping. It is also desirable to provide a new dielectric construction with individual injection molded polymeric components.